Hypochlorite bleaching composition and method of making



HYPOCHLORITE BLEACHING COMPOSITION AND METHOD OF MAKING Homer L. Robson, Lewiston, N. Y., assignor to Olin Mathieson Chemical Corporation, a corporation of No Drawing. Application February 21, 1955 Serial No. 489,729

14 Claims. (Cl. 252-95) This invention relates to novel compositions of matter and their utilization in laundry bleaching. More particularly, it relates to an improved form of sodium carboxymethylcellulose and to improved calcium hypochlorite compositions which may be added as dry products direct to the laundry wash wheel in the presence of soap.

In commercial laundering, most of the goods to be washed are composed of white cotton goods which the laundry operator wishes to deliver in a clean, sterile condition with a high degree of whiteness. Bleaching is an important step in achieving this result. In commercial laundry practice, the washing cycle consists of many changes of water, usually about ten. The laundry cycle starts with a break in which the clothes are washed in a wheel in an alkaline liquor which may or may not contain soap. After several minutes of washing in this liquor, the laundry wheel is drained and several washings follow with sufiicient soap to give detergency. Normally about four such suds treatments are employed with the wash, liquor being drained from the wheel after each suds. Bleaching is usually done in the last suds. Following the last suds, usually about four rinses are employed, followed by a sour and blue operation.

The reaction of calcium salts with soap solutions to form calcium soaps is well known. In normal laundry work the soil and soap are usually sufliciently removed at the second rinse to given no formation of calcium soap curds. In soil-free solutions, no curd will form on addition of 50 to 100 parts per million of available chlorine as calcium hypochlorite, even though the latter contains an added amount of quicklime to effect desiccation. In certain laundry operations, such as linen supply, however, the clothes may be much more soiled than is normal and the soil may be of a type which promotes the formation of calcium soap curds. With such goods, laundry operators frequently add two to four times as much bleach in an effort to offset the soiled condition of the cloth. Under these conditions, objectionable soap curd specks on the cloth are formed. Calcium soaps under some conditions also form insoluble macroscopic curds which suggest objectionable dirt and frequently do carry a minor portion of dirt. In addition, rancidity may develop from the calcium soaps on the washed clothes if they are stored for long periods of time. Not all of the calcium soap will appear in the form of specks but some may be in a molecularly dispersed form, distributed throughout the cloth which, when in limited amounts, may not be-objectionable. The presence of soap specs or flees, however, amounting to less than one half of one percent on the dry weight of the cloth, may make the washing treatment unsatisfactory by laundry standards. Frequently, laundry standards require a complete absence of calcium soap deposits in the form of spots. For these reasons commercial laundries have avoided calcium hypochlorite compositions in bleach operations. Any of the methods available to laundries for the utilization of sodium hypochlorite solutions are cumbersome but they have been preferred because they avoid the danger of calcium soap formation.

Sodium carboxymethylcellulose has been used for some time in laundry rinse waters to minimize or prevent the formation of lime soaps on the addition of a calcium salt to the solution. However, the separate addition of a further component to the bleaching step is objectionable in laundry operation. It is desirable to supply a single composition to laundry operations which when added to the rinse water gives satisfactory results particularly in avoiding the formation of lime soaps'without the necessity of adding a further component.

The incorporation of organic materials with calcium hypochlorite, especially high test hypochlorite containing upwards of 50 percent available chlorine, may result in flammable mixtures. Sodium carboxymethylcellulose is particularly objectionable since it is generally light and fiuffy and readily segregates from a relatively dense product such as calcium hypochlorite when the mixture is packaged and subjected to mechanical agitation as in shipment. Furthermore, the incorporation of moist ingredients in hypochlorite mixtures usually deleteriously afiects stability. The known instability of calcium hypochlorite preparations when compounded with materials containing water requires that the sodium carboxymethylcellulose must be brought to a dry state prior to inclusion with calcium hypochlorite in mixtures intended for laundry purposes. However, it is known that some methods of drying sodium carboxymethylcellulose preparations impair their usefulness in laundry work. Many laundries now use sodium carboxymethylcellulose preparations as a means of improving whiteness retention, and for this purpose a grade is supplied which normally contains 60 to percent by weight of actual sodium carboxymethylcellulose and from 6 to 8 percent by weight of water with the balance being largely sodium chloride with some by-products of the manufacture. Material with this water content is reasonably fast dissolving and is effective in improving whiteness retention. However, this material cannot be directly incorporated with hypochlorites due to its moisture content. If the same material is dried in an ordinary manner, such as by holding at C. in a current of air until dry, both its rate of solution and its ability to improve whiteness retention are impaired. The desired properties can be restored by dissolving the dried material in water and re-precipitating it, and then drying to the usual 6 to 8 percent of water. This loss of effectiveness on drying has been ascribed to a curling or folding of the chains of the polymer so that less of the effective solubilizing groups are exposed to the solution. Some uncurling or unfolding takes place when the dried material is dissolved in water at laundry temperatures, such as F., but this action is slow in comparison with the short cycles employed by laundry machines, which usually run from 3 to 5 minutes and are rarely as long as 10 minutes for rinse cycles.

The first novel product of the present invention comprises a spray-dried composition containing sodium carboxymethylcellulose suitable for use in preparing stable calcium hypochlorite compositions and for other purposes hereinafter described. Thus, when sodium carboxymethylcellulose is dissolved or dispersed in water with suitable proportions of sodium sulfate, the solution can be spray-dried to form beads containing about 0.5 to 4 percent of water by weight. These beads can be vacuum-dried to a product containing about 0.1 to 0.3 percent of water by weight which retains the desirable fast dissolving characteristics of the sodium carboxymethylcellulose and its ability to improve whiteness retention. In addition and in contrast to previously available forms of sodium carboxymethylcellulose, the product EXAMINER prepared by spray drying followed by vacuum drying is also compatible with solid hypochlorites and stable mixtures can be prepared therefrom. The fast dissolving properties are retained perhaps because the spray-drying process is too fast for the polymer chains to fold into a less active state, or because the long, thin laths of sodium sulfate, together with grains of undissolved sodium sulfate, provide surfaces upon which the chains are extended.

The novel product which has simply been spray dried to contain about 0.5 to 2 percent of water by weight is useful as such. Many commercial laundries add preparations of sodium carboxymethylcellulose at the start of the rinse step. This addition improves whiteness retention of the cloth by preventing redeposition of soil suspended from the work during the suds bath. Some sodium carboxymethylcellulose additions have a beneficial effect on the feel or hand of the finished work. This last effect may also be obtained with other additives. Previously available sodium carboxymethylcellulose preparations have serious faults as additives to the laundry wheel. When poured, dumped or sprinkled into the wheel, they may swell and form slow dissolving lumps. Sometimes these lumps adhere to working surfaces of the wheel as a gummy deposit, which is considered objectionable. The swollen material may be in small grains, somewhat resembling tapioca, or in much larger lumps. To avoid formation of this lumped or gelled material, sodium carboxymethylcellulose intended for the laundry trade is normally specially processed, to put it in im proved physical form. It may be diluted with inerts which aid in dispersing the material on addition to the wheel and reduce the lump forming tendency. It may be granulated, as by compressing or tabletting and then crushing to a desired sieve size. However, all of the treatments heretofore tried minimize but do not remove the tendency of the sodium carboxymethylcellulose to swell on contact with the laundry water and to form adherent deposits in the wheel. In contrast to this, the spray dried product when containing about 0.5 to 2 percent by weight of water shows good dispersion and ordinarily goes into solution without formation of lumps. To obtain this effect it is necessary that the beads be of adequate density to sink and disperse, and that fines be limited in amount. A suitable material would carry 10 to 25 percent of sodium carboxymethylcellulose by weight and consist of grains mostly of 30 to 50 mesh size with less than ten percent passing a 100 mesh screen (U. S. Standard screens). Large portions of fines may cause the spray dried beads to fioat temporarily and some lumping may result. The performance in any case is superior to that of an equal grade of sodium carboxymethylcellulose mechanically mixed with a diluent.

The manufacture of the sodium carboxymethylcellulose compositions of the present invention thus comprises, as a first step, spray-drying an aqueous mixture of sodium carboxymethylcellulose and sodium sulfate. Suitable concentrations for feed to commercial spray driers are about 5 percent of sodium carboxymethylcellulose and 15 percent of sodium sulfate (Na SO in water. The aqueous mixtures spray dried can contain from about 2 to percent of sodium carboxymethylcellulose, three to nine parts by weight of sodium sulfate per part by weight of the sodium carboxymethylcellulose and are selected to yield spray dried beads containing from about 10 to 25 percent of the carboxymethylcellulose and correspondingly from about 90 to 75 percent of sodium sulfate (Na SO the percentages being by weight.

The spray drying operation can conveniently be operated to remove fines as dust so that the spray dried composition contains largely particles through 30 mesh and retained on 100 mesh (U. S. Standard screens). When screen-analyzed in the laboratory such a product will contain less than 10 percent by weight fines through 100 mesh. The spray dried composition may be screened if necessary, due to poor operation of the spray drier, to reduce the content of fines. The bulk specific gravity of the spray dried composition is about 0.35 or higher. This is sufficient to avoid segregation in shipment of mixtures with calcium hypochlorite having a bulk specific gravity of about 0.74.

-In preparing the mixture for spray-drying, it is advantageous to make up a saturated solution of sodium sulfate at 50 to C. and then to disperse the sodium carboxymethylcellulose therein. A portion of finely ground anhydrous sodium sulfate may be added and the slurry is then spray-dried using drying air inlet and outlet temperatures of about 400 550 F. and 200-275 F., respectively. The product thus prepared appears to be more active than that obtained when the sodium carboxymethylcellulose is first dissolved, the sodium sulfate being added later. Several grades of sodium carboxymethylcellulose are commercially available and they differ primarily in the viscosity of solutions prepared from them. The low viscosity (about 50 centipoises or less for a 2 percent by weight aqueous solution at 25 (3.), low molecular weight types are more effective in delaying curd formation, and it is preferable to use low viscosity grades in the preparation of the products of the present invention.

To convert the spray-dried sodium carboxymethylcellulose product containing about 0.5 to 4 percent by weight of water to a product suitable for compounding with solid hypochlorites, it is vacuum dried to contain about 0.1 to 0.3 percent by weight of water under sufficiently .mild conditions that the stability of its physical form is not impaired. It will stand a maximum drying temperature of about C. for up to 24 hours and higher temperatures for shorter times. When the temperature is about C., the time should not exceed about 30 minutes and temperatures up to C. can be used provided the drying time is less than one minute. A temperature of about 80 to 90 C. is preferred, limiting the time to about two hours.

Other cellulosic derivatives having similar physical and, particularly solubility properties can be used in place of sodium carboxymethylcellulose. An example is sodium carboxymethylhydroxyethyl cellulose. Where these are of low viscosity they are also amenable to treatment according to the present invention to produce similar products.

The second novel product of the present invention comprises calcium hypochlorite, sodium carboxymethylcellulose in the novel form just described which is substantially stable toward solid hypochlorites, and diluent salts, particularly sodium sulfate. A minor proportion of a desiccant, for example, quicklime is frequently added. This composition of the present invention is stable and resists segregation of the components and is entirely safe in shipment and in use. It does not produce objectionable precipitates of calcium soaps when added to soapy water, provides a single composition more convenient than sodium hypochlorite and utilizes the cheaper calcium hypochlorite.

The proportion of the novel sodium carboxymethylcellulose-containing spray-dried and vacuum dried product in these compositions is suitably about 10 to 40 percent by weight of the final composition. The proportion of high test calcium hypochlorite used can vary from about 40 to 65 percent by weight but advantageously approximately about 45 to 55 percent. Quicklime or other suitable desiccant, for example, sodium monoxide, potassium carbonate or anhydrous calcium chloride suitably about 2 to 10 percent by weight, may be added but is not essential to insure stability in storage. Advantageously flake salt is added as a diluent to aid in the rapid dispersing and solution of the product when added to a laundry wash wheel. In addition, the composition may contain other compatible ingredients such as sodium silicate, sodium bicarbonate, soda ash and the like. It is at times desirable to incorporate a detergent of the synthetic organic type or other additives to facilitate rinsing or to add to the effectiveness of the compositions.

The calcium hypochlorite compositions useful in the manufacture of the products of the present invention are preferably those prepared from a stable calcium hypochlorite, high in available chlorine and low in lime and calcium chloride. A preferred calcium hypochlorite product can be prepared as described in U. S. Patent 1,787,048. Commercial products of this type usually contain about 70 percent by weight available chlorine. However, calcium hypochlorite products containing about 35 percent or more of available chlorine may be used according to the present invention.

Example I An a ueous solution of 5p;

absence of any sodium carboxymethylcellulose, curds were observed to form in one-half minute. When ordinary, commercially available sodium carboxymethylcellulose equal to 5 parts per million was added before adding the calcium hypochlorite preparation, curds formed in 1 to 2 minutes, and the curds were finer and less likely to leave objectionable spots on cloth. When this experiment was repeated, using a sodium carboxymethylcellulose which had been dried at 125 C., the curd time was about onehalf minute and the curds were of the large and sticky type which form objectionable spots on cloth. However, when a spray dried mixture of sodium sulfate and carboxymethylcellulose prepared as described in Example I was added prior to adding the calcium hypochlorite mix- 5 ture, in amounts sufiicient to give 5 to 7.5 parts per milrcent by weight of tion at 25 C.) and percent by weight of sgdiggt sulfate (anhydrous) iIv'as mried using drying an" irii'f'i'nd outlet temperatures oi about 500 F. and 250 F., respectively, to yield beads containing about percent by weight of sodium carboxymethylcellulose, about 75 percent by weight of sodium sulfate and about 1 percent by weight of water. The product was screened,

drie cf a'fiwvicttum 'drie'dbeads were separately screened and the fractions between and 100 mesh selected. A mixture was prepared by blending 52 parts by weight of the HTH, 3 parts by weight of quicklime, 16 parts by weight of the spray dried beads, 3 parts by weight of sodium tripolyphosphate and 26 parts by weight of flake salt. This gave a mixture containing 38 percent available chlorine and 4 percent sodium carboxymethylcellulose, plus the inert ingredients. This mixture did not segregate in shipment and did not ignite below 180 C.

When washing normally soiled clothes in a commercial laundry, the second rinse water contains about 100 to 200 parts per million of soap. Direct addition of calcium hypochlorite to such rinse water preferably containing not over 150 parts per million of soap, to provide about 50 parts per million of available chlorine, does not result in immediate precipitation of calcium soaps. Addition of the composition prepared in accordance with the preceding paragraphs in this example, however, results in no precipitation of calcium soap in the form of soap specks. Further rinses and souring by conventional practice gives a final load entirely free of soap specks. When washing heavily soiled goods, more soap is used and an extra rinse is usually provided. In this case it is preferable to add the calcium hypochlorite preparation of this example to the third rinse.

Example II In one series of tests, a rinse water containing 150 parts per million of soap, 150 parts per million of sodium metasilicate and a large amount of soil, of known ability to promote the formation of calcium soap curds, was placed in a stirred apparatus and sufiicient of a calcium hypochlorite preparation was added to give 50 parts per million of available chlorine in the solution. In the lion of sodium carboxymethylcellulose in the solution, the curd time was increased to 4 minutes. Again the curds were finely divided and less objectionable than those formed in the absence of the sodium carboxymethylcellulose.

Example Ill Under conditions of soil, soap andsodium silicate similar to those used in Example II, the amount of calcium hypochlorite preparation was increased to 100 parts per million in the solution. In this case the curd formation time was only one-half minute when no sodium carboxymethylcellulose was added. When 10 parts per million of sodium carboxymethylcellulose dried at 125 C. was added, no improvement was produced and the time for curd formation was still one-half minute. With a spray dried preparation of sodium carboxymethylcellulose and sodium sulfate, prepared as described according to the present invention, the time for curd formation was increased to one minute and finer curds were formed.

5 The sodium carboxymethylcellulose concentration in each By weight of sodi case was 10 parts per million.

I claim:

1. A composition of matter suitable for use in laundering consisting essentially of from 10 tmpercenp by weight of a material selected from the group consisting I of sodium carboxymethylcellulose and sodium carbgx me thylhyfiicfiiyah ylfeilifdse and from 9 t 9 l5 percept sulfate, said composition biting been prepared by 's'piay drying an aqueous mixture of from 2 to 10 percent by weight of said material and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 0.5 to 4 percent by weight of water.

2. A composition according to claim 1 in which said material is sodium carboxymethylcellulose.

3. A composition according to claim 2 in which the spray dried product contains from 0.5 to 2 percent by weight of water and in which said composition consists of spray dried grains mostly of 30 to 50 mesh size with less than 10 percent passing a 100 mesh screen (U. S. Standard screens).

4. A method for the preparation of a composition suitable for use in laundering which comprises spray drying an aqueous mixture consisting essentially of water, from 2 to 10 percent by weight of a material selected from the group consisting of sodium carboxymethylcellulose and sodium carboxymethylhydroxyethyl cellulose and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 10 to 25 percent by weight of said material, from to 75 percent by weight of sodium sulfate and from 0.5 to 4 percent by weight of water.

5. A process according to claim 4 in which said material is sodium carboxymethylcellulose.

6. A process according to claim 5 in which the spray drying is conducted to provide a spray dried product containing from 0.5 to 2 percent by weight of water.

7. A method for the preparation of a composition suitable for use in laundering which comprises spray drying an aqueous mixture consisting essentially of water,

from 2 to 10 percent by weight of a material selected from the group consisting of sodium carboxymethylcellw lose and sodium carboxymethylhydroxyethyl cellulose and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 10 to 25 percent by weight of said material, from 90 to 75 percent by weight of sodium sulfate and from 0.5 to 4 percent by weight of water and having a screen size of from 30 to 100 mesh (U. S. Standard screens) and vacuum drying the spray dried product at a temperature up to about 150 C. to provide a vacuum dried product containing from about 0.1 to 0.3 percent by weight of water.

8. A process according to claim 7 in which said material is sodium carboxymethylcellulose.

9. A composition of matter consisting essentially in admixture of from 4ilm oafiiflpcmcnttbymmeightmofna calcium hypochlorite containing at least 35 percent available chlorine, from 2 to 10.pe r c nt by weight of calcium, oxide and from l to 40 percent by weight of a spray drie d and vacuum dried pfo' dgct consisting essentially of from 10,19, 25 percent by weight of a material selected from the group consisting of sodium carboxymethylcellulose and sodium. ylhydroxyethyl cellulose and from 90 to 75 percent by wargnr'ar some; sulfate, said spray mum dried ronncr'cematmn from 0.1 to 0.3 percent by weight of water, having a screen size of from 30 to 100 mesh (U. S. Standard screens), and having been prepared by spray drying an aqueous mixture of from 2 to percent by weight of said material and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 0.5 to 4 percent by weight of water and vacuum drying the spray dried product at a temperature up to about 150 'C.

10. A composition of matter consisting essentially of in admixture from 40 to 65 percent by weight of a calcium hypochlorite containing at least 35 percent available chlorine, from 2 to 10 percent by weight of a desiccant stable to calcium hypochlorite and from 10 to 40 percent by weight of a spray dried and vacuum dried product consisting essentially of from 10 to 25 percent by weight of a material selected from the group consisting of sodium carboxymethylcellulose and sodium carboxymethylhydroxyethyl cellulose and from 90 to 75 percent by weight of sodium sulfate, said spray dried and vacuum dried product containing from 0.1 to 0.3 percent by weight of water, having a screen size of from 30 to 100 mesh (U. S. Standard screens), and having been prepared by spray drying an aqueous mixture of from 2 to 10 percent by weight of said material and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 0.5 to 4 percent by weight of water and vacuum drying the spray dried product at a temperature up to about 150 C.

11. A composition of matter consisting essentially of in admixture from 40 to 65 percent by weight of a calcium hypochlorite containing at least 35 percent available chlorine and from 10 to 40 percent by weight of a spray dried and vacuum dried product consisting essentially of from 10 to 25 percent by weight of a material selected from the group consisting of sodium carboxymethylcellulose and sodium carboxymethylhydroxyethyl cellulose and from 90 to percent by weight of sodium sulfate, said spray dried and vacuum dried product containing from 0.1 to 0.3 percent by weight of water, having a screen size of from 30 to 100 mesh (U. S. Standard screens), and having been prepared by spray drying an aqueous mixture of from 2 to 10 percent by weight of said material and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 0.5 to 4 percent by weight of water and vacuum drying the spray dried product at a temperature up to about 150 C.

12. A composition of matter suitable for use in laundering consisting essentially of from 10 to 25 percent by weight of a material selected from the group consisting of sodium carboxymethylcellulose and sodium carboxymethylhydroxyethyl cellulose and from to 75 percent by weight of sodium sulfate, said composition having been prepared by spray drying an aqueous mixture of from 2 to 10 percent by weight of said material and from 3 to 9 parts by weight of sodium sulfate per part by weight of said material to provide a spray dried product containing from 0.5 to 4 percent by weight of water and vacuum drying the spray dried product at a temperature up to about 150 C. to provide a vacuum dried product containing from about 0.1 to 0.3 percent by weight of water.

13. A composition according to claim 12 in which said material is sodium carboxymethylcellulose.

14. A composition of matter consisting essentially of in admixture from 40 to 65 percent by weight of a calcium hypochlorite containing at least 35 percent available chlorine, from 2 to 10 percent by weight of calcium oxide and from 10 to 40 percent by weight of a spray dried and vacuum dried product consisting essentially of from 10 to 25 percent by weight of sodium carboxymethylcellulose and from 90 to 75 percent by weight of sodium sulfate, said spray dried and vacuum dried product containing from 0.1 to 0.3 percent by weight of water, having a screen size of from 30 to mesh (U. S. Standard screens), and having been prepared by spray drying an aqueous mixture of from 2 to 10 percent by weight of sodium carboxymethylcellulose and from 3 to 9 parts by weight of sodium sulfate per part by weight of said sodium carboxymethylcellulose to provide a spray dried product containing from 0.5 to 4 percent by weight of water and vacuum drying the spray dried product at a temperature up to about C.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Surface Active Agents, by Schwartz et al., pages 102, 379, Interscience Publishers, Inc., New York (1949). 

12. A COMPOSITION OF MATTER SUITABLE FOR USE IN LAUNDERING CONSISTING OF FROM 10 TO 25 PERCENT BY WEIGHT OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF SODIUM CARBOXYMETHYLCELLULOSE AND SODIUM CARBOXYMETHYLHYDROXYETHYL CELLULOSE AND FROM 90 TO 75 PERCENT BY WEIGHT OF SODIUM SULFATE, SAID COMPOSITION HAVING BEEN PREPARED BY SPRAY DRYING AN AQUEOUS MIXTURE OF FROM 2 TO 10 PERCENT BY WEIGHT OF SAID MATERIAL AND FROM 3 TO 9 PARTS BY WEIGHT OF SODIUM SULFATE PER PART BY WEIGHT OF SAID MATERIAL TO PROVIDE A SPRAY DRIED PRODUCT CONTAINING FROM 0.5 TO 4 PERCENT BY WEIGHT OF WATER AND VACUUM DRYING THE SPRAY DRIED PRODUCT AT A TEMPERATURE UP TO ABAOUT 150*C. TO PROVIDE A VACUUM DRIED PRODUCT CONTAINING FROM ABOUT 0.1 TO 0.3 PERCENT BY WEIGHT OF WATER. 